Glow plug igniter



Jan. 16, 1962 J. J. LAWSER GLOW PLUG IGNITER Filed Oct. 29, 195"!JJLAWSER 6 II77VENTOR BY 7 Ff grron/vexs United States Patent O3,017,541 GLOW PLUG IGNITER John J. Lawser, Dearborn, Mich, assignor toFord Motor Company, Dearborn, Mich, a corporation of Dela- Ware FiledOct. 29, 1957, Ser. No. 693,060 3 Claims. (Cl. 31'798) This inventionrelates to a glow plug igniter and more particularly to a glow plugigniter which is especially adapted for use in the combustion chambersof gas turbine engines.

Although not so limited, the glow plug igniter of this invention issuitable for use in the heating means of the Elastic Fluid Power Plantdisclosed in copending application Serial Number 650,446, filed April 3,1957, in the names of Willis M. Clark, Jr., and Benjamin T. Howes, andassigned to the assignee of the present invention. Glow plugs used inthis type of power plant must ignite a mixture of fuel and air whichflows past the glow plug at quite high rates from the impetus of thecompressor turbine. This high rate of flow past the igniter has alwaysbeen a problem as this raw mixture of fuel and air tends to cool theigniter below ignition temperatures.

Under normal starting conditions, the resistance wire of a glow plugigniter must reach very high temperatures, on the order of 1500 to 3000degrees F., for a period of ten seconds or more in order to ignite thefuel-air mix ture. After combustion has been initiated and the glow plughas been de-energized, the end of the glow plug element will be exposedto high temperatures, for example, from 1400 to 1800 degrees F for longperiods of time while the engine is operating.

The present invention provides a glow plug igniter which is admirablysuited for use in a gas turbine engine working under the above operatingconditions. Briefly, the invention comprises a glow plug igniter witha'body which is adapted to be affixed to the combustion chamber of a gasturbine engine. An electrical conductor, electrically insulated from thebody of the glow plug, is mounted within the body along with arefractory support which is adapted to support a resistance wire. Thebody of the glow plug serves as one electrical terminal for theresistance wire while the electrical conductor serves as the otherterminal. Preferably, the refractory support has a helical groovepositioned in its outer periphery and the resistance wire, which ispreferably helically coiled, is wrapped around this support member inthe helical grooves, thus providing a large surface area of resistancewire for use in igniting the combustible mixture. The resistance wire isconnected at one end to the body and the other end to the electricalconductor, both of these connections preferably being made aconsiderable distance from the end of the glow plug which is adapted toprotrude into the combustion chamber. This feature provides forelectrical connections in a region which is relatively cool duringengine operation.

The end of the glow plug body preferably extends beyond the end of therefractory support and protrudes farther into the combustion chamberthan does the resistance Wire. The body has a series of aperturespositioned therein in the vicinity of the resistance wire and preferablynear the end of the refractory support. Such a structure prevents theresistance wire from being unduly chilled by the fiow of raw fuel andair past the glow plug prior to ignition, while the apertures locatedadjacent the resistance wire causes turbulence of this fuel and airmixture adjacent the heated resistance wire which aids materially in theinitiation of combustion.

An object of the present invention is the provision of a glow plugigniter for use in the combustion chamber of a gas turbine engine.

3,017,541 Patented Jan. 16, 1962 A further object of the invention isthe provision of a glow plug igniter for use in the combustion chamberof a gas turbine engine in which a large surface of heated resistancewire is exposed to a combustible mixture.

Another object is to provide a glow plug igniter for use in a gasturbine engine in which the resistance wire is protected against unduechilling from the flow of an unignited combustible fuel mixture pastsaid glow plug prior to ignition.

A further object is the provision of a glow plug igniter for use in agas turbine engine in which a structure to produce turbulence ofunignited fuel-air mixture about the resistance wire is provided.

Still another object of the invention is the provision of a glow plugigniter for use in a gas turbine engine in which the electricalconnections are made remote from the end of the glow plug which extendsinto the combustion chamber of the engine.

Other objects and attendant advantages of the present invention willbecome more apparent as the specification is considered in connectionwith the drawings in which:

FIGURE 1 shows a partial longitudinal sectional view of one embodimentof the invention;

FIGURE 2 is an end view of the embodiment shown in FIGURE 1;

FIGURE 3 shows a partial longitudinal sectional view of anotherembodiment of the invention;

FIGURE 4 is a partial longitudinal sectional view of another embodimentof the invention.

Referring now to the drawings there is shown in FIG- URES 1 and 2, oneembodiment of the present invention in which the numeral 10 designatesthe glow plug body as a whole. The glow plug may have a threaded portion11 which is adapted to be fitted into the combustion chamber of a gasturbine engine, a portion 12 having a smaller diameter than the threadedportion 11, and a portion 13 of still smaller diameter which forms asleeve about the igniter unit. As shown, the glow plug body has twointernal bores 14 and 15 with the upper bore 14 having a smallerdiameter than the bore 15, thereby forming a shoulder 16.

An inner assembly comprising an electrical conductor generallydesignated by the numeral 17 and a refractory support 22 is fitted intothe body 10. The electrical conductor 17 is provided with a threaded endportion 18 and an enlarged end portion 21.

The refractory support 22 is preferably made of alumina, A1 0 and has ahelical groove 23 formed in its outer surface, and a central bore 24positioned therein. The refractory support is suitably positioned in abore 25 in the enlarged end portion 21 of the'electrical conductor 17. Aresistance wire having a double twisted lead 26 is secured to theenlarged portion 21 of the electrical conductor 17 and said doubletwisted lead extends through the bore 24 to the end of the refractorysupport 22 at which point one of the leads terminates. The remaininglead is then formed into a helically coiled portion 27 which ispositioned in the helical groove 23 of the refractory support 22. Theend of the resistance wire is then suitably connected to a metallicsleeve 28 which fits in the bore 15 of the body 10 and against theshoulder 16. The sleeve 28 is electrically insulated from the electricalconductor 17 by means of a refractory insulating washer 31, preferablymica, positioned between said sleeve and the enlarged end portion 21 ofthe electrical conductor 17.

A suitable insulating sleeve 32 made, for example, of refractoryceramic, may be positioned in the bore 14 between the electricalconductor 17 and the body 10. The whole inner assembly comprising theelectrical conductor 17, the refractory support 22 and the resistancewire is suitably secured in the body 10* by means of a nut 33 which isthreaded down on the threaded portion 13 of the electrical conductor 17.An insulating washer 34, preferably made of mica, is positioned betweenthe body and the nut 33 to maintain the electrical conductor 17 and thebody 10 electrically isolated, so that the electrical conductor 17 canserve as one terminal of the glow plug and the body It) can serve as theother terminal. The upper portion of the body member 10 may be providedwith a hexagonal shaped portion 36 which may be used in tightening theglow plug igniter in a combustion chamber of a gas turbine engine.

It will be noted that the end of the body portion 13 extends beyond theend of the refractory support 22 and also beyond the helically coiledresistance wire 27. A plurality of apertures 35 may be positioned aroundthe periphery of the portion 13 of the glow plug body. The body portion13 shields the resistance wire from the cooling effect of the unignitedfuel-air mixture prior to ignition while the apertures provide a meansfor producing desired turbulence about the resistance Wire which aidsmaterially in the ignition of the combustible mixture.

Provision of the helically coiled wire wound in the helically coiledgrooves on the refractory support, provides a maximum of resistance wireexposure to the unignited fuel-air mixture, while connecting theresistance Wire to the electrical conductor and the glow plug bodyremote from the end of the glow plug which protrudes into the combustionchamber keeps this connection, which may be of the soldered type, fromexposure to elevated temperatures.

Provision of the shoulder 16 in the body member 10 and the enlarged endportion 21 of the electrical conductor '17 together with the sleeve 2%and insulating washer 31, provides a gas tight seal between the bodymember and the inner assembly of the glow plug igniter. As the gaspressure in the combustion chamber rises, the enlarged end portion 21 ofthe electrical conductor 17 will be forced against the insulating washer31, Sleeve 28 and the shoulder 16 thereby forming a gas tight seal andpreventing separation of the inner assembly from the glow plug body.

FIG. 3 depicts a glow plug igniter similar to the one disclosed inFIGURES 1 and 2, except that the intermediate portion of the bodybetween the two internal bores 14 and 15 forms a tapered portion 46. Theenlarged end portion 51 of the conductor 17 is also tapered tocomplement the shape of portion 46. Similarly, sleeve 58 and insulatingmember 61 are so shaped to fit the contours of the enlarged end portion51 and the tapered portion 46. This glow plug igniter provides all ofthe advantages of the igniter disclosed in FIGURES l and 2, and inaddition, provides a greater surface area between tapered por tion 46 ofthe body 10 and the tapered enlarged end portion 51 of the electricalconductor 17, thereby providing a larger sealing area for the preventionof gas leaks between the inner assembly and the body of the glow plug.

In the embodiment illustrated by FIG. 4, there is shown a glow plugigniter body generally designated by the numeral 110, having a threadedportion 111, a portion of reduced diameter 112, and a hexagonal shapedportion 113 which is adapted to receive a tool for securing the igniterbody within the combustion chamber of a gas turbine engine. The body hasa first internal bore 114, a second internal bore 115, and a thirdinternal bore 116 of smaller diameter than either the bore 114 or 115.Preferably, the transition between the bore 114 and 116 is made by meansof a tapered portion 117. A refractory support 118 having a portion ofreduced diameter 121 and a tapered portion 122 is positioned within thebores in the body 110 with the tapered portion 122 being complimentaryin shape to the tapered portion 117. The portion of reduced diameter issimilar to the refractory support 22 shown in FIGURES l and 3, and has ahelical groove 123 positioned around the periphery thereof.

A sleeve 124 made of an electrical conductive material is positionedaround the tapered portion 122 of the refractO-ry support 118 and mayextend down to encompass part of the portion of reduced diameter 121.This sleeve makes electrical contact with the tapered portion 117 of thebody and a resistance wire 129 is electrically connected thereto. Aswith the embodiments of FIGURES 1 and 2 and FIG. 3, this resistance wireis preferably helically coiled and positioned within the groove 123 inthe refractory support.

The refractory support has an internal bore 130 which is adapted toreceive an electrical conductor 125. The electrical conductor has aninternal bore 126 which is aligned with a second internal bore 127 inthe refractory support member. A twisted lead 128, which is an extensionof the helically coiled resistance wire 129, extends through the bore127 in the refractory support member and through'the bore 126 in theelectrical conductor where it is electrically connected to the conductorat 131 by brazing or spot welding. As in the other embodiments of theinvention a second twisted lead may be employed with lead 128 and mayextend from the connection 131 to the end of the refractory supportwhere it terminates.

The lower portion 112 of the body member 110 extends beyond the end ofthe refractory support member 11 8 and beyond the helically coiledresistance wire 129 to prevent undue cooling of the resistance wire bythe flow of the unignited combustible mixture, and is provided with aplurality of apertures 132 which cause desired turbulence as previouslydiscussed. Positioned at thetop of the body is a flange 133 whichextends to engage the refractory support 118 and to prevent the pressurein the combustion chamber from separating the refractory support 118from the body 110. An insulating material 134, such as magnesium oxide,may be positioned between the refractory support 118 and the body 110.

All of the embodiments of the invention provide the advantages discussedparticularly in connection with the embodiment disclosed in FIGS. 1 and2. In addition, means are provided in all three embodiments to preventthe gas pressure developed in the combustion chamber from separating theinner assembly from the body of the glow plug igniter.

It will be understood that the invention is not to be limited to theexact construction shown and described, and that various changes andmodifications may be made without departing from the spirit and scope ofthe invention, as defined in the appended claims.

What is claimed is:

l. A glow plug for use in the combustion chamber of a gas turbine enginecomprising, a body for mounting the glow plug igniter within saidcombustion chamber, said body having a first internal bore extendingfrom one end of said body to a point intermediate the ends thereof and asecond internal bore extending from the other end of said body to saidpoint intermediate the ends thereof thereby forming a shoulder in saidbody, an electrical conductor having an enlarged end portion, saidelectrical conductor being positioned within said first internal borewith the enlarged end portion being positioned within said secondinternal bore, insulating material positioned between one end of saidenlarged end portion and said shoulder, a refractory support having ahelical groove positioned in the periphery thereof being supported bythe other end of the enlarged end portion of said electrical conductor,and a helically coiled resistance wire positioned in the helical grooveof said refractory support and being electrically connected at one endto said body and atthe other end to said electrical conductor, said bodyextending axially beyond said refractory support and said helicallywound resistance Wire at the end of said body which is adapted to bepositioned within said combustion chamber, said body being imperforatefrom one end thereof to a position immediately adjacent the end thereofwhich extends beyond said refractory support and said helically woundresistance wire into said combustion chamber, said body having aplurality of apertures positioned around the periphery thereofimmediately adjacent said end adapted to be inserted in the combustionchamber and immediately adjacent the end of said refractory support andsaid electrical resistance wire, the enlarged end portion of saidelectrical conductor engaging the shoulder in said body formed betweensaid first internal bore and said second internal bore through saidinsulating material thereby preventing the fluid pressure which isdeveloped within said combustion chamber from separating said refractorysupport and said helically coiled resistance wire from said body.

2. A glow plug igniter for use in the combustion chamber of a gasturbine engine comprising, a body portion for mounting the glow plugigniter within said combustion chamber, said body having a firstinternal bore extending from one end of said body to a pointintermediate the ends thereof and a second internal bore of largerdiameter than said first internal bore extending from the other end ofsaid body and terminating short of said first internal bore, a taperedportion joining said first and said second internal bores, an electricalconductor having an enlarged tapered end portion, the enlarged taperedend portion being positioned within the tapered portion of said body,electrical insulating material being positioned between said taperedportions with the remainder of the electrical conductor being positionedwithin said first internal bore and being electrically insulated fromsaid body, a refractory support having a helical groove positioned inthe periphery thereof being supported by the enlarged end portion ofsaid electrical conductor, a helically wound resistance wire positionedin the helical groove in said refractory support and electricallyconnected at one end to said electrical conductor and at the other endto said body, said body extending axially beyond said refractory supportand said helically wound resistance wire at the end of said body whichis adapted to be positioned within said combustion chamber, said bodybeing imperforate from one end thereof to a position immediatelyadjacent the end thereof which extends beyond said refractory supportand said helically wound resistance wire into said combustion chamber,said body having a plurality of apertures positioned around theperiphery thereof immediately adjacent to said end adapted to beinserted in the combustion chamber and immediately adjacent the end ofsaid refractory support and said electrical resistance wire, the taperedenlarged end portion of said electrical conductor engaging the taperedportion of said body through said electrical insulating material therebypreventing the fluid pressure which is developed within said combustionchamber from separating said refractory support and said helicallycoiled resistance wire from said body.

3. A glow plug igniter for use in the combustion chamber of a gasturbine engine comprising, a body portion for mounting the glow plugigniter within said combustion chamber, said body having an internalbore, a refractory support having an enlarged end portion and a reducedend portion positioned within said bore, said enlarged end portionhaving an internal bore, said reduced end portion also having aninternal bore, an electrical conductor positioned within the internalbore of the enlarged end portion of said refractory support, the smallerend portion of said refractory support having a helically groovepositioned therein, a helically coiled resistance wire positioned insaid helical groove and being electrically connected at one end to saidbody, a twisted extension of the other end of said resistance wireextending through the internal bore in the reduced end of saidrefractory support and being electrically connected to said electricalconductor, said body extending axially beyond the end of the reduced endof said refractory support and said helically coiled resistance wire, atthe end of said body which is adapted to be positioned within saidcombustion chamber, said body being imperforate from one end thereof toa position immediately adjacent the end thereof which extends beyondsaid refractory support and said helically wound resistance wire intosaid combustion chamber, said body having a plurality of aperturespositioned therein immediately adjacent the smaller end of saidrefractory support and said helically coiled resistance wire, said bodyhaving a flange extending therefrom over said internal bore and engagingthe enlarged end portion of said refractory support for preventing thefluid pressure which is developed within said combustion chamber fromseparating said refractory support and said helically coiled resistancewire from said body.

References Cited in the file of this patent UNITED STATES PATENTS1,453,461 Hoffman May 1, 1923 1,826,788 Huber Oct. 13, 1931 1,887,730Macrae Nov. 15, 1932 1,914,284 Palmer June 13, 1933 1,956,586 Palmer May1, 1934 1,957,762 Dorner May 8, 1934 2,385,699 Fox Sept. 25, 19452,761,947 Rice Sept. 4, 1956 2,776,394 Cuny Jan. 1, 1957

